1. Field of the Invention
The present invention relates to a method of manufacturing an amorphous silicon-based thin film photoelectric conversion device, and particularly to a method of manufacturing thereof to achieve an excellent performance as an amorphous silicon-based thin film photoelectric conversion device together with improvements in production cost and efficiency.
2. Description of the Background Art
An amorphous silicon based solar cell is a typical thin film photoelectric conversion device. An amorphous photoelectric conversion material is usually prepared by a plasma CVD method at a film-forming temperature as low as about 200.degree. C., so that it can be formed on an inexpensive substrate, e.g., of glass, stainless steel, organic film, and thus expected as a preferable material for low-cost photoelectric conversion devices. Furthermore, since amorphous silicon has a large absorption coefficient for the visible-light range, a solar cell using an amorphous photoelectric conversion layer of a thickness at most 500 nm has achieved a short-circuit current at least 15 mA/cm.sup.2.
A p type semiconductor layer, an i type amorphous photoelectric conversion layer, and an n type semiconductor layer that compose the amorphous silicon-based solar cell are usually produced by plasma CVD respectively and the pressure in a conventional plasma CVD reaction chamber is 1 Torr or less.
U.S. Pat. No. 5,646,050, for example, discloses a method of manufacturing an amorphous silicon-based solar cell under a relatively high pressure condition. According to this document, an amorphous silicon layer in the amorphous silicon-based solar cell is fabricated on conditions that the pressure is greater than 1.0 Torr and at most 10 Torr, and the dilution ratio of dilution gas to raw material gas ranges from 5:1 to 200:1.
If the pressure is 1 Torr or less, the deposition rate decreases.
According to the conditions for depositing the amorphous silicon layer disclosed in U.S. Pat. No. 5,646,050, the amount of the dilution gas relative to the raw material gas is excessive. In other words, the amount of the raw material gas relative to the dilution gas is too small. As a result, the amount of the raw material gas supplied into the plasma CVD reaction chamber is insufficient, leading to degradation of the film deposition rate.